The invention relates to a gear in accordance with the preamble of claim 1. A gear with an interior tooth arrangement, as well as having a cup-shaped, base body with a rotary shaft, is claimed as described in PL 169808 B1. A driven input member and an output member are seated, and rotatable, around a rotary shaft in the base body. The output member comprises a rotating body with a cross section which is circular transversely to the rotary shaft. Two toothed wheels meshing with the interior gear wheel, as well as means for converting planetary movements of the toothed wheels into rotary movements of the output member, are arranged between the rotating body and the bottom of the cup-shaped base body. The input member is seated in the rotating body and in the bottom. The rotating body is seated in the base body and on the input member. Disadvantages arise from accessibility at only one end, in particular in view of a driving and a driven member, as well as from the complexity and uncontrollability of mounting in a cup which is closed on one side.
A gear with a base body which has an interior tooth arrangement is known from EP 0 474 897 A1 in which a driven input shaft, as well as an output shaft, are rotatably seated in the base body. An output member is connected, axially displaceable, with the output shaft. The output member includes two rotating bodies, which are arranged at a distance from each other and have a circular cross section. The input and the output shafts are oriented perpendicularly with the two rotating bodies. The rotating bodies are fixedly connectable, or respectively connected, with each other. Two toothed wheels, which mesh with the interior toothed wheel, as well as means for converting planetary movements of the gear wheels into rotary movements, are arranged between the rotating bodies. The output member is supported in a bearing-free manner in the radial direction in respect to the base body by means of the toothed wheels which mesh with the inner tooth arrangement. Support of the output member in the axial direction in regard to the base body does not exist, or is respectively also embodied to be bearing-free, so that axial movements of the output member are only maintained by contact with a cover, the base body, or with the flanks of the inner tooth arrangement. Low efficiency of the gear is disadvantageous here, along with the expected heavy wear on the output member, which is arranged in a bearing-free manner in the base body.
A gear is known from WO 95/22017, which has a base body with front sides, in the shape of a hollow cylinder with an interior tooth arrangement and with a rotating shaft. In the base body, a driven input member and an output member are seated and rotatable around the rotating shaft. The output member includes two rotating bodies, which are arranged at a distance from each other and have a cross section which is circular transversely in regard to the rotating shaft. The rotating shaft is located perpendicularly with respect to the two rotating bodies. The rotating bodies can be, or are, fixedly connected to each other. At least one toothed wheel, which meshes with the interior tooth arrangement, as well as means for changing planetary movements of the toothed wheel into rotating movements of the output member, are arranged between the rotating bodies. The input member is seated on both sides in the rotating bodies of the output member, which is in turn seated with both sides in the hollow cylinder-like base body.
Here, both rotating bodies are seated directly on, or in the base body. In this way, the adjustable force which keeps the two rotating bodies together simultaneously acts on the seating of the two rotating bodies. As a result, twisting of the seating, increased wear, and heating occurs, and in the worst case scenario, the gear is blocked. Moreover, the assembly of the gear is cumbersome because the parts arranged between the rotating bodies must be inserted after the rotating bodies have been arranged in the base body. Furthermore, forces acting on the gear, in particular exterior forces acting in the axial direction, are transmitted to the interior of the gear leading to fluctuating loads and fatigue.
In this case, seating has been designed in such a way that one radial bearing supports one rotating body, respectively, and at one end face of the base body against radial forces acting in a standard way in regard to the rotating shaft. Furthermore, one axial bearing supports respectively one of the two rotating bodies arranged on both sides of the base body, and on one end face of the base body, against axial forces directed toward the base body in the direction of the rotating shaft. The input member is seated in principle in the same way on the rotating bodies. The axial bearings which support the input member in the rotating bodies against axial forces are, however, arranged exactly in the opposite way as the axial bearings for supporting the rotating bodies on the base body. This means that the input member is seated by means of one axial bearing on the two rotating bodies, respectively, which transmits axial forces acting on the input member (in the direction of the rotating shaft) away from the base body to the rotating body respectively arranged in the force direction on the outside of the base body. Combined axis-radial bearings can selectively fulfill both functions simultaneously.
Fundamentally, without a connection between the two rotating bodies, the gear would fall apart. To prevent this, the two rotating bodies of the output member are releasably connected to each other by connecting elements such as screws. Here, the connecting elements simultaneously fulfill several functions. For one, they make sure that the same number of revolutions and the same torques are applied to both power take-off sides constituted by the two rotating bodies, and that they regularly work the sides of the gear. Since the connecting elements connect the rotating bodies to each other, they also keep the parts of the gear located in the base body along the rotating shaft together. Essentially, these parts are one or several toothed wheels which mesh with the interior toothed wheel, the input member itself, and the means for converting planetary movements of the toothed wheel(s) into rotating movements of the output member. Moreover, the connecting elements transmit axial forces acting on the input member and/or the output member to that rotating body whose axial seating is capable of transferring the respective axial forces to the base body again. Such axial forces, or respectively pairs of axial forces, can also be generated, for example, by moments acting on the input and/or output member transversely in respect to the rotating shaft. The connecting elements additionally prevent the bearings arranged between the output member and the input member, as well as between the output member and the base body, from falling out by pressing the rotating bodies on both sides against the front side bearing surfaces of the base body.
If particularly quiet running and high gearing (and transfer quality of the drive output at the drive and power take-off sides) is to be achieved, particular difficulties arise from the multiple functions of the connecting elements. For example, to transmit axial forces and/or pairs of forces acting on the base body via the input and/or output members and the bearings of the rotating bodies, the connecting elements must press the two rotating bodies together with pre-stress because otherwise these forces would pull the rotating bodies apart. If the rotating bodies were pulled apart, a dependable and precise operation of the gear would no longer be assured. The creation of a correspondingly strong pre-stress demands a correspondingly large dimensioning of the connecting elements. However, connecting elements of large dimensions require structural space and increases the weight of such a gear. The bearings between the input member and the rotating bodies, as well as between the rotating bodies and the base body, should not be allowed to strongly press together in the axial direction by the pre-stress. Otherwise the gear will be excessively heated because of frictional losses in the bearings. However, since the tolerance of the parts arranged between the rotating bodies along the rotating shaft, are added to the tolerance of the rotating bodies and the base body, the above requirements are contraindicated.
Because a disadvantageous summing up of the tolerances of the parts arranged between the rotating bodies may occur, the parts can also be pressed together in the event a large pre-stress of the rotating bodies is required. This can lead to large frictional losses between the parts, causing the gear to become overheated and destroyed. In the worst case scenario, these parts can even cease to function. Also since, in the case of a disadvantageous summing up of the tolerances of the rotating bodies and the base body, and/or the rotating bodies and the input member, the axial bearings between the rotating bodies and the base body, and/or the axial bearings between the input member and the two rotating bodies, may be pressed together if a large pre-stress of the rotating bodies is required. This can also lead to large frictional losses in the axial bearings causing the gear to overheat and fail prematurely. Finally, in this regard, it is important to note that the rotating bodies can even sag concavely.
A further disadvantage resulting from the multi-function of the connecting elements is that the pre-stress applied via the connecting elements can slacken during the operation of the gear, particularly since the connecting elements are continuously stressed.
The disadvantages of the prior art can therefore be summed up as follows:                a) the mutual dynamic stress of the rotating bodies,        b) all parts of the output member must be produced with especially high precision and matched to the corresponding parts of the base body, which leads to a long and disadvantageous chain of tolerances,        c) the tilting resistance of the output member is limited by the elasticity of the connecting means (screws) extending in the axial direction,        d) the long startup time of the gear.        
The object of the invention is to provide relief here, and in particular to further develop the gear in accordance with the species without unreasonable constructive outlay, and in such a way that increased torsional strength, as well as greater power density, is achieved with the same measurements, but with simpler manufacture of the individual parts and simpler assembly of the gear.
The object is attained by means of the characteristics of claim 1. Accordingly, a gear in accordance with the invention is comprised of a hollow cylinder-like base body having an interior tooth arrangement, as well as a rotating shaft and end faces. A driven input member and output member are rotatably seated in the base body. The output member is comprised of two rotating bodies which can be, or respectively are, connected to each other in a secure manner to avoid twisting. The rotating bodies have a cross section which is circular transversely in respect to the rotating shaft. At least one toothed wheel is arranged between the rotating bodies. The toothed wheel preferably meshes with the interior tooth arrangement. Means for converting planetary movements of the toothed wheel into rotating movements of the output body are arranged between the rotating bodies. The forces which hold the output member of the gear together are independent of the seating forces acting between the output member and the base body.
So that the forces holding the output member together are independent of the seating forces acting between the output member and the base body, it has been preferably provided that the axial forces holding the output member together will be, or respectively are, applied between the rotating bodies of the output member. The axial seating forces acting between the output member and the base body will be, or respectively are, only applied between one of the two rotating bodies of the output member and the base body.
The axial forces keeping the output member together will be, or respectively are, preferably supplied by means acting between the rotating bodies of the output member.
The axial seating forces acting between the output member and the base body will be, or respectively are, supplied with the aid of means for acting only on one of the two rotating bodies of the output member.
It is evident that the invention can be accomplished in any event at the point at which, in a conventional planetary gear, the compact output member is regularly seated with two rotating bodies extending parallel to, and at a distance between each other, in such a way that, of the two rotating bodies, only a single rotating body is directly seated in or on the base body. The two rotating bodies constitute the end faces of the output member and the base body. The exterior forces acting on the output member in the course of operation, at least in the axial direction, are for all practical purposes completely taken up by the rotating body seated directly in or on the base body. The other rotating body located on the other side of the base body is for all practical purposes not subjected to exterior forces and, in particular, is not subjected to exterior forces acting in the axial direction. This rotating body also is not in working contact with the base body. The only important force acting on the rotating body (which is not rotatably seated on or in the base body, or is only indirectly rotatably seated on or in the base body, or is only directly rotatably seated in or on the base body as a support against radial forces), is the static force produced by the connecting means, normally screws, for keeping the output member—which is designed as a unit—together. With this constellation, it can be assured that the working forces acting indirectly or directly, at least in the axial direction on the rotating body seated in or on the base body, are not transferred to the other rotating body. As a result, the only areas of the gear which must be worked at high precision are the contacting and bearing surfaces of the base body, the rotating body seated indirectly in or on the base body, and the holding body, which are provided for seating the output member. Since these surfaces are accessible without problems from one direction of the gear, it is possible to cut the production time of the gear in half. A further advantage of the steps in accordance with the invention is that the active interior space of the gear is noticeably increased by the special positioning of the seating elements, therefore considerably increasing the output of the gear without changing the exterior dimensions, and the weight of the gear is reduced.
In general, the basic idea of the invention can be applied to all types of planetary gears. In accordance with the invention, preferably only one of the rotating bodies is seated directly on the base body, at least with respect to the axial forces, for obtaining the independence of the seating forces and of the forces keeping the rotating bodies together. Furthermore, a ring-like holding body, which can be fixedly connected with one end face, is preferably provided, on which the rotating body, which is directly seated on the base body, is supported via bearing means. The holding body can be preferably embodied as a thick-walled, and easy to work, pipe section, whose two end faces merely need to be grounded and provided with suitable openings for screws, without any problems. The rotating body seated directly on the base body can furthermore be supported on the base body via the same, or other, seating means.
In comparison with the prior art, the gear in accordance with the invention has the advantage of connecting elements, normally screws, that are load-free to the greatest extent because of the one-sided seating, at least in respect to the axial forces, of the output member in the area of only one rotating body. Now, a transfer of force from the seated rotating body to a frame supporting the gear takes place while completely bypassing the second rotating body which is, at least in respect to the axial forces, not seated, and therefore bypassing the connecting elements which connect the two rotating bodies to each other.
Besides a remedy of the disadvantages known to exist in the prior art, the gear in accordance with the invention has the additional advantage of being considerably more easy to produce and assemble. Among other things, this is caused by the seating means for seating the rotating bodies directly in or on the base body, so that for support, at least in regard to the axial forces, they need only be arranged on one side of the base body. Since these seating means are preferably the only connection between the parts arranged between the rotating bodies and the base body, the gear in accordance with the invention can be easily produced in successive steps. Initially, all parts located between the rotating bodies can be mounted and positioned with respect to each other by connecting the two rotating bodies. Subsequently, the entire block consisting of the rotating bodies, and parts arranged between them, can be arranged in the base body. Here, it is no longer necessary, as in the prior art, for the rotating bodies and the parts arranged between them to be mounted in the base body. In accordance with the invention it is only necessary, for example, in the course of mounting the preassembled block, to insert the bearing means between the base body and the seated rotating body. In this way, it is possible to shorten the assembly time, resulting in fewer assembly errors.
For example, as described in WO 95/22017, the means for converting planetary movements of the toothed wheel into rotary movements of the output body can be a transformation element in the form of a cross, which is arranged, displaceable in two directions, between the toothed wheel and the rotating bodies. However, the means for converting planetary movements of the toothed wheel into rotary movements of the output body can also, as described in WO 2006/058743, be eccentric ring-shaped sleeves, which are arranged between recesses on the toothed wheel or on the rotating body, or pins arranged on the rotating body or on the toothed wheel, which project into recesses in the toothed wheel or the rotating body.
It is important to stress that, for fastening of the output body to the base body, one of the rotating bodies is preferably rotatably seated directly on or in the base body.
For fastening the output body on the base body, one of the rotating bodies can be rotatably seated directly on or in the base body for support, at least against axial forces, while the other rotating body is not seated in or on the base body, or is only indirectly rotatably seated in or on the base body or, for support against radial forces, is directly rotatably seated in or on the base body.
Preferably, one of the rotating bodies are rotatably seated directly on or in the base body, both for support against axial forces, as well as for support against radial forces.
Preferably, the rotating body which is rotatably seated directly on or in the base body is supported via seating means on the holding body, which can be, or is, fixedly connected to the one end face.
An advantageous embodiment of the invention provides that the seating means be arranged in the area of the end face on which the holding body is arranged. To this end, in contrast to the prior art, a gear in accordance with the invention is produced with substantially improved and simpler accessibility of the bearing surfaces for the rolling bodies of the seating means. A simplified positioning of the seating means is also produced.
Another advantageous embodiment of the invention is that bearing surfaces are provided (at least on the rotating body which is directly seated on or in the base body, and on the base body) for rolling bodies constituting the seating means for the rotating body in the base body. For example, the bearing surfaces can be in the form of flat areas and/or grooves with polished and hardened surfaces.
An additional advantageous embodiment of the invention provides that at least the seating means, as well as preferably associated bearing surfaces employed for supporting the rotating body seated directly on or in the base body against forces extending in the axial direction toward the interior tooth arrangement in the area of a means, used for the conversion of planetary movements of the toothed wheel into rotary movements of the output member and arranged on the same side of the interior tooth arrangement as the rotating body directly seated on or in the base body, are arranged radially offset toward the outside. An advantage resulting from this is that, because the rolling bodies constituting the seating means are displaced radially outward in the area of, for example, a conversion element, which converts the planetary movements of the toothed wheel into rotary movement of the output member, a gear of particularly compact exterior dimensions and in particular of a short structural length is created.
A preferred embodiment of the invention provides that at least the seating means—as well as the associated bearing surfaces continuously extending around the rotating shaft—which are intended for supporting the rotating body seated directly on or in the base body against forces extending in the axial direction, are arranged offset from the interior tooth arrangement in the direction of the rotating shaft with respect to a means used for converting planetary movements of the toothed wheel into rotary movements of the output member, and which is arranged on the same side of the interior tooth arrangement as the rotating body which is directly seated on or in the base body. An advantage arising from this embodiment is an increase in the available interior space for the movable parts located between the rotating bodies. This takes place because the rolling bodies constituting the seating means are axially offset with respect to the parts arranged between the rotating bodies and are arranged outwardly displaced. Because of this, the gear can be designed to be more rugged while having the same exterior diameter, since a larger structural space is available in the base body in the axial direction for the conversion elements, for example.
Another preferred embodiment of the invention provides that the seating means are embodied as ball-shaped rolling elements, which support the rotating body seated directly on or in the base body in the axial (and radial) direction, and which are arranged in a common ring-shaped space formed by the holding body, the base body, and the rotating body seated directly on or in the base body, and defined by bearing surfaces continuously extending around the rotating shaft. An advantage resulting from this arrangement is that only a single space is required for transmitting all axial and radial forces acting on the rotating body, via common rolling elements, to the base body and to the holding body, which is connected with the base body by means of fastening elements.
An additional preferred embodiment of the invention provides for the seating elements to be embodied as cylinder-shaped rolling elements, which support the rotating body directly seated on or in the base body in the axial (and radial) direction, and which are arranged in a common ring-shaped space defined by the holding body, the base body, and the rotating body. Moreover, the cylinder-shaped rolling elements are directly seated on or in the base body and is respectively inclined by 45° with respect to the rotating shaft and by the bearing surfaces continuously extending around the rotating shaft, and are arranged in the area of the front on which the holding body is arranged. An advantage of this embodiment is that, in contrast to the ball-shaped rolling elements, the cylinder-shaped rolling elements can support greater loads because they rest in a line shape, instead of a point-shaped, manner on the respectively assigned bearing surfaces.
In accordance with a preferred embodiment of the invention, the gear has a cover which protects the movable parts in the interior of the gear against dirt on the side facing a rotating body which is not-seated, or only indirectly seated on or in the base body, or seated only for support against radial forces directly on or in the base body.
The cover preferably has a central opening, through which the input member is introduced, for example, to connect to a drive motor.
To prevent the penetration of dirt into the gear, a circumferential seal may be arranged in the area of the central opening between the cover and the input member.
In a particularly preferred embodiment, a bearing surface for seating bodies is formed on the cover, on which the input member is seated with its side facing a rotating body which is not-seated, or only indirectly seated on or in the base body, or seated only for support against radial forces directly on or in the base body. In this way, no axial forces act on the non-seated rotating body, and the connecting elements connecting the two rotating bodies to each other need not transmit any axial forces between the rotating bodies.
A circumferential seal should be provided between the rotating body directly seated on or in the base body, which prevents the penetration of dirt into the gear on the driving side.
In accordance with a preferred embodiment of the invention, the side of the gear facing the rotating body directly seated on or in the base body is embodied as the power take-off side, and the side of the gear facing the rotating body which is not-seated, or only indirectly seated on or in the base body, or seated only for support against radial forces directly on or in the base body, is embodied as the driving side of the gear. Experience has shown that the loads on the power take-off side are greater than on the driving side, for which reason it is advantageous to design the power take-off side of the seated rotating body in such a way that the moment acting on the seating elements in this way, and the resultant pairs of forces, are reduced.